Reenforced porcelain tooth crown



Jan. 11,1938. A. BARRETT ET AL I REENFORCED PORCELAIN TOOTH CROWN FiledNov. 30, 1935 Patented Jan. 11, 1938 @Nttfifi STATEfi PATENT DFFEEEApplication November 30, 1935, Serial No. 52,316

Claims.

- This invention relates to reenforced dental tooth crowns and methodsof making the same. Heretofore difiiculties in non-metallic tooth crownshave been experienced by reason of break- 5 age thereof due to bendingor labial stresses, or other uneven strains, or washing out. of cement,

' and for other causes.

It has been diflicult to reenforce such crowns,

particularly if made of porcelain, because the fusion temperature ofthis material is very high and because it will not strongly adhere tometal or bond therewith. The logical reenforcement material is platinum,and still better, an alloy of platinum and iridium, for superiorstrength, but it is impossible to cast a reenforcement of such metal,due to its high melting temperature.

With the foregoing considerations in mind, and realizing the extremelybrittle character of porcelain, the thinness required of the wall of theporcelain crown, and further, that every crown must be fitted to aparticular tooth so that quantity production methods cannot'be readilyused, we have devised the comparatively simple and inexpensive structureand method herein disclosed.

The invention provides a crown of porcelain or other like material andcan be made by any standardized technique and without requiring .thatthe tooth be devitalized. An impression is first made as in the ordinaryconstruction of a porcelain crown, then a model and die are made whichshould duplicate the exact conditions in the mouth. Over the die aplatinum foil matrix may be adapted, and upon the latter acoping orshell of iridio-platinum foil. This shell or reenforcement is perforatedsufficiently to allow for subsequent bonding with the porcelain andwithout unduly weakening the structure. This shell or reenforcement ismade sufficiently loose to allow for the disposition of a layer ofporcelain between it and the first platinum matrix. An outside layer ofporcelain is then applied over the reenforcement, and the entire massremoved from the die and placed in a furnace to fuse the porcelain onthe reenforcement. Then the crown is finished to blend with. the otherteeth in th mouth.

, Our invention in structure and method as above generally describedfulfills the requirements for a recnforced porcelain crown, overcomesthe difficulties mentioned, and is highly advantageous in use.

Other objects and advantages of the invention will become apparent asthe specification proceeds.

With the aforesaid objects in view, the inven tion consists in the novelcombinations and ar- 'rangements of parts hereinafter described; intheir preferred embodiments, pointed out in the subjoined claims, andillustrated in the annexed 5 drawing, wherein like parts are designatedby the same reference characters throughout the several views.

In the drawing:

Figure" 1 is a perspective view of an incisor 10 tooth with our improvedcrown, shown in dotted lines, applied thereto.

Fig. 2 is a longitudinal sectional view showing the manner of preparingthe tooth.

Fig, 3 is an enlarged vertical sectional view of a 15 crown embodyingthe invention and as applied to a tooth.

Fig. 4 is a view in elevation with parts in section showing thereenforcing element.

Fig. 5 is a vertical sectional view showing a modification of theinvention.

The advantages of the invention as here outlined are best realized whenall of its features and instrumentalities are combined in one and thesame structure, but, useful devices may be 25 produced embodying lessthan the whole.

It will be obvious to those skilled in the art to which the inventionappertains, that the same may be incorporated in several different con-.structions. The accompanying drawing, there- 30 fore, is submittedmerely as showing the preferred exemplificatidn of the invention.

Referringin detail tothe drawing, l0 denotes a dental tooth crown orjacket embodying the invention. The same may be applied in any suitableor conventional manner to a tooth II with the portion l2 thereof, whichprotrudes from the gum (not shown) being undercut to a reduced size andto provide an annular lip I3 which may be in the regularly acceptedrelation to the gum. 40 The crown It] may be secured to the portion 42as by cement or the like.

The crown I0 is characterized by a reenforcement which extendsthroughout a major portion or the entireextent of the crown, and whichmay 45 be confined to one side'or face of the porcelain, but ispreferably disposed mainly of in substantial part within the wall of thecrown. Since porcelain is brittle and of relatively low tensilestrength, but high in compressive strength, we 50 use a reenforcementwhich is high in tensile strength and is so uniformly disposedthroughout the crown wall, or in such strong bonded relation therewith,that the combined qualities of porcelain and reenforcement supplementeach other to 55 prevent breakage of the porcelain, despite thecomparative pliability of the reenforcement itself.

Fig. 4 shows the reenforcement l4 whichis in the nature of a jacket orshell having continuous side and bottom walls I5, l6, and being open atthe top as at "5. This shell may be madeof platinum or of aplatinum-iridium alloy. The metal used may be in the nature of a foil,so as to be pliable and easily workable.

If desired, the shell 14 is perforated substantially throughout withholes of any suitable size and shape as indicated at H, for permittingan integral union or bond between the inner and outer porcelain layers[8, 19.

Preferably, the shell l4 may have a reenforce--v ment, for example, aband, fold or hem 20 along the rim or margin of the opening l6.

For a further understanding of the structure the method of making thesame willnow be described. We first construct a matrix corresponding tothe tooth portion l2. Then the perforated metal foil is worked over thematrix by pressing, folding and otherwise manipulating the foil. Thisshaping is preferably done loosely to leave a clearance or space for theinner porcelain layer l8. These operations necessarily result in theoverlapping of certain parts of the foil atthe bottom at 2| and at theposterior of the shell as at 22. At the same time the hem 20 is foldedover and formed or otherwise applied. A female dieelement may beapplied, if desired, to tightly conform the jacket to the matrix.Finally, the fold portions as at 2|, 22 are soldered, as with platinumsolder, so that the bottom and side walls become continuous. The shellI4 is now complete.

In certain cases, it may be preferred to tightly H receive the shell,prior to soldering, between male and female dies of suitable size toassure a requisite uniformity or smoothness in the shell orreenforcement.

To complete the crown, porcelain may be applied to the inner and outersurfaces, andthe crown then heated to fuse the porcelain, thus causingthe layers l8, I!) to provide a uniform one piece structure whichextends through the perforations l1 and which unites over the rim of thecrown opening as at 23 to thus cause the reenforcement to be whollyencased by the porcelain.

In certain instances a second coating of an especially opaque porcelainmay now' be applied, and fused on the crown to wholly conceal thereenforcement or any effect thereof.

The completed crown l0 may now be applied to the tooth II.

In Fig. 5 is showna crown 24 illustrating a form that is modified inthat the reenforcing hem or bead is inwardly directed as at 25 tomaintain the outer face of the reenforcement as smooth as possible.slightly outwardly form the hem 25 to lie more nearly in the planes ofthe side walls, and thus to assurefevenness of the porcelain layers,both internally and externally.

It is noted that at the fold sections as at 20, 2|, and 25 certain ofthe perforations may be closed due to the overlapping, but the fusedporcelain can still enter the perforations. If required, theseperforations, particularly at the rim reenforcement may be punched ordrilled as at 26 so that the porcelain may be positively bonded throughat the rim portions.

The mode of operation of the invention will now be described. It will beborne in mind that In certain cases, it may be desired tobreakage ofporcelain crowns most frequently occurs in relative proximity to the lipor shoulder l3, and may occur either in the longitudinal or transversedirection. Further such breakage is most general at the labial portionsof the crown. Sometimes some of the cement dissolves out, and breakagemay occur due toresulting unevenness of strains. In general, we havefound that the breakage is due to bending strains produced by stressesat the lingual side of the tooth by reason of biting engagement orstress with a complementary tooth. Furthermore, the toothportion towhich the crown is attached, generally possesses some degree offlexibility which further promotes breakage of the ordinary porcelaincrown. According to our invention, the crown is reenforced throughout sothat, under a bending stress, not only is all annular tension taken up,but longitudinal tensions, including those at various angles are whollyassumed by the reenforcement; and since every bending strain producesits counterpart of compression, the porcelain bears such stresses, andsince the reenforcement extends throughout the porcelain, and is inbonded relation therewith, the interacting tensions and compressionsfully balance each other. At the crown rim, the reenforcement possessesadded strength but it will be understood that the hem or fold partthereat as at 20, 25 may be omitted. Likewise the perforations may incertain cases be omitted, since the porcelain wholly ,encases thereenforcement particularly at the rim thereof. With the use ofperforations, it will be appreciated that the inner porcelain layer maysometimes be omitted, as the outer layer may fuse into the perforationsand thus bond the porcelain with the metallic reenforcement. Theperforated shell hereindescribed is representative of any foraminous orskeletonized structure that may be used for a like purpose.

We claim:

l. A tooth crown having an inner foil of a platinum-like metal and anouter layer of a porcelain-like material, said inner foil havingperforated side walls, and said outer layer having portions fused intosaid perforations, said outer layer completely surrounding said innerfoil.

2. A tooth crown having an inner layer of a platinum-like foil, and anouter layer of a porcelain-like material, said inner layer havingirregularities defining points of attachment for the outer layer, thelatter having fused engagement with the inner layer at said points, saidouter layer completely surrounding said inner layer. v

3. A tooth crown having an intermediate perforated foil of aplatinum-like material, said foil having bottom and side walls, andinner and outer layers of a porcelain-like material fused upon saidintermediate foil and integrally united through said perforations.

4. A tooth crown including an outer layer of a refractory non-metallicmaterial having a relatively high compressive strength and a relativelylow tensile strength, and an inner foil of metallic material having arelatively high tensile strength, the inner foil being so thin as to becomparatively pliable, both said layer and said foil being pre-- formedto the shape of the tooth portion to which the crown is to be attachedand extending substantially throughout the wall area of the crown, andsaid layer and sheet being directly permanently united throughout thesaid area to constitute a unit possessing the combined strengths of bothsaid materials, said foil having irregularities in its side wallsproviding points of attachment for said layer, and said layer beingfirmly interlocked with said foil by projections extending from saidlayer and having fused engagement with said foil at the points definedby said irregularities, said layer further completely surrounding saidfoil.

5 A tooth crown including an inner layer of a platinum-like foilmaterial providinga continuous annular side wall, said wall beingperforated and comprising an annular reenforcing band layer around andover said band and into said 5 perforations, to constitute a unitarytooth crown.

ADOLPH BARRETT. LEO HIRSCHHORN.

